Wrong Amount Debited

In the middle of June a consultant called me and helped me with my upgrade and told him that I want to stick to what I've been paying which is R360.00 per month. On the 15th of July I was debited R1244.60 and we didn't agree on that. I've been calling mtn customer care and the call center agents have been taking me from pillar to post telling me about the 'Éarly termination charge of my contract".

I honestly feel mtn ****** me. I want to be refunded my money otherwise I'm leaving the network.